I´d like to do this in my network:

Internet
|
Gateway Linux(2 lan cards + IPCHAINS)
|
IIS(Internal IP)

Redirect all www access from linux to IIS but this command don´t work for me
-> ipmasqadm portfw -a -P tcp -L IPLINUX 80 -R IPIIS 80

What should I do?

I use 2 NIC's

Eth0 = 192.168.1.1 (Local network)
Eth1 = Pump (Cable Modem)

I masq all Internet addresses from internal net through eth0 to eth1 to the web.

This is the script i use (its a very simple firewall)

/sbin/depmod -a
/sbin/modprobe ip_masq_ftp
/sbin/modprobe ip_masq_raudio
/sbin/modprobe ip_masq_irc
/sbin/modprobe ip_masq_quake 26000, 27000, 27910, 27960
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/ip_always_defrag
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
echo "1" > /proc/sys/net/ipv4/ip_masq_udp_dloose
/sbin/ipchains -M -S 7200 10 160
/sbin/ipchains -A input -j ACCEPT -i eth1 -s 0/0 67 -d 0/0 68 -p udp
/sbin/ipchains -P forward DENY
/sbin/ipchains -A forward -i eth1 -s 192.168.1.0/24 -j MASQ

Just run this script at startup.

Make sure u have all the modules installed.
Redhat and a few others come pre-configured.

Hope this helps